The long-term goal of this research project is to understand the mechanism of cell adhesion, and involves a multidisciplinary approach using biochemical, immunological, and microscopic methods. During the past year we have characterized the FN-2 BHK cell adhesion variant and found that it is deficient in the cell-substratum contact process. That is, cell adhesion receptors are present on the surface of these cells, but the receptors cannot reorganize so as to engage in cooperative interactions. A high molecular weight glycoprotein found on parental cells is absent from the FN-2 variant and will be characterized further in the future. We also have prepared 5 monoclonal antibodies to BHK cells and are in the process of studying the effects of these antibodies on cell adhesion. Analysis of cell cytoskeletal responses to different sized fibronectin-coated beads revealed reorganization of actin and alpha actinin in response to the binding of large (5 micron beads) but not small (1 micron beads). This reorganization appeared to reflect differences in cell deformation in response to the beads. The large beads induced the formation of large cell ruffles while the small beads interacted with cell microvilli. Studies are now underway to determine whether different subsets of cell membrane coponents interact with the large and small beads. (A)